Tetra-hydro alkyl substituted indanes are key ingredients in the synthesis of musk and woody fragrance ingredients. These compounds are formed from selective hydrogenation of alkyl substituted indanes in the presence of platinum group metal catalyst. Conventionally, these hydrogenation reactions are conducted in batch reactors such as high pressure autoclaves. The reaction kinetics of fast hydrogenation are often limited by external mass transfer of gas through the liquid to the catalyst surface on account of the poor gas/liquid/solid contact provided by these reactors. As a result, reactions take much longer time than kinetically required, leading to side reaction(s) and formation of significant amount of byproduct(s). Besides, these reactions are highly exothermic in nature. Poor heat transfer may lead to non-uniform temperature distribution in the reactors, which may also have deleterious effects on the reactor performance such as the formation of hot-spots and thermal runaway conditions.
In recent years, the use of microreactors, also known as microchannel reactors, for enhancing the performance of fast hydrogenation reactions has sparked intensive efforts among both academic and industrial participants. Microreactors with their small transverse dimensions possess extremely high surface to volume ratios and consequently exhibit enhanced heat and mass transfer rates. The small transverse dimensions of microreactors enable fast transport across fluid layers thus reducing the reaction time and providing greater selectivity and higher product yield. Besides, the use of a continuous microreactor for highly exothermic reactions enables uniform temperature control throughout the reactor and prevents the occurrence of side reactions that may result due to the existence of temperature gradients inside the reactor. Several patents and articles in the literature disclose the use of microreactor technology for various hydrogenation reactions that have shown improved product yield by taking advantage of enhanced heat transfer or mass transfer rates. Microreactors not only help to improve the product yield and Space Time Yield or productivity but also offer cleaner, safer and more energy efficient technology to the perfumery industry which is constantly searching for safe, high-throughput production methods with reduction in energy consumption and minimization of liability risks compared to the existing batch reactors.
The present invention involves using the advantages of microreactors for the synthesis of tetra-hydro alkyl substituted indanes known as THPMI from the selective hydrogenation of alkyl substituted indanes known as PMI, wherein THPMI constitutes a mixture of 2 isomers: tetra-hydro penta-methyl indane and tetra-hydro ethyl tri-methyl indane, and PMI constitutes a mixture of 2 isomers: penta methyl indane and ethyl tri-methyl indane.